<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <script src="./lib/jquery.js"></script>
</head>

<body>

  <input type="file" id="file1" />
  <button id="btnUpload">上传文件</button>

  <br />
  <img src="./images/loading.gif" alt="" style="display: none;" id="loading" />

  <script>
    $(function () {
      // 监听到Ajax请求被发起了
      $(document).ajaxStart(function () {
        $('#loading').show()
      })

      // 监听到 Ajax 完成的事件
      $(document).ajaxStop(function () {
        $('#loading').hide()
      })

      $('#btnUpload').on('click', function () {
        var files = $('#file1')[0].files
        if (files.length <= 0) {
          return alert('请选择文件后再上传！')
        }

        var fd = new FormData()
        fd.append('avatar', files[0])

        // 发起 jQuery 的 Ajax 请求，上传文件
        $.ajax({
          method: 'POST',
          url: 'http://www.liulongbin.top:3006/api/upload/avatar',
          data: fd,
          processData: false,
          contentType: false,
          success: function (res) {
            console.log(res)
          }
        })
      })
    })
  </script>

</body>

</html>